Cleavage - Radial Cleavage

One of the hallmarks of deuterstome
development is that early cleavage divisions are radial.
In contrast, protostomes typically
display spiral cleavage. While
these classifications are certainly huge generalizations, they nevertheless
point to some of the fundamental differences between different phyla regarding
early development. Play the movie at the below right to get a sense for
the difference between these two cleavage patterns in two generalized embryos.